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A2 Biology OCR June 2015 Revision Thread

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Original post by Missy1x
Does anyone have the June 2014 f214 paper


http://www.thebiotutor.com/past-papers3.html
Original post by GregJ94
In the book, in section 1.1.9, it refers to low level stimuli when talking of summation and filtering out signals. I thought that with the all-or-nothing nature of impulses that all action potentials were of the same strength or 'level'? When it says low-level stimulus, is that the same as infrequent?


This confused me for a long time when I came across this passage too. I believe it is meaning that low level stimuli can be amplified by spatial summation. So where 2+ neurones converge to a single postsynaptic neurone, each single neurone would not release enough acetylcholine to stimulate an action potential in the postsynaptic neurone, but the two presynaptic neurones together release enough acetylcholine to stimulate action potential in postsynaptic neurone.

Hence the low level stimuli that caused each presynaptic neurone to fire has been amplified to cause a postsynaptic action potential.

Hope that helps.


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Original post by Hilton184
This confused me for a long time when I came across this passage too. I believe it is meaning that low level stimuli can be amplified by spatial summation. So where 2+ neurones converge to a single postsynaptic neurone, each single neurone would not release enough acetylcholine to stimulate an action potential in the postsynaptic neurone, but the two presynaptic neurones together release enough acetylcholine to stimulate action potential in postsynaptic neurone.

Hence the low level stimuli that caused each presynaptic neurone to fire has been amplified to cause a postsynaptic action potential.

Hope that helps.


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Hi :smile: do you think temporal summation would also amplify low level stimuli?
Original post by Lighfy
Hi :smile: do you think temporal summation would also amplify low level stimuli?


Yeah I do, I don't get why temporal summation has a distinct name though because temporal summation if I am correct is just lots of action potential from a presynaptic neurone stimulating the postsynaptic neurone.. Which means a high frequency of action potentials which is how the strength of a stimulus is determined anyway!


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When talking about receptors in the plasma membrane.

Do we say

the receptors in the plasma membrane.

Or

the receptors on the plasma membrane.

As ridiculous as this sounds I've seen this penalised at least once, but I can't remember which one they wanted or which paper it was or anything!


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Original post by Hilton184
When talking about receptors in the plasma membrane.

Do we say

the receptors in the plasma membrane.

Or

the receptors on the plasma membrane.

As ridiculous as this sounds I've seen this penalised at least once, but I can't remember which one they wanted or which paper it was or anything!


Posted from TSR Mobile

On the plasma membrane.
Original post by Hilton184
When talking about receptors in the plasma membrane.

Do we say

the receptors in the plasma membrane.

Or

the receptors on the plasma membrane.

As ridiculous as this sounds I've seen this penalised at least once, but I can't remember which one they wanted or which paper it was or anything!


Posted from TSR Mobile


Pretty sure you say they are 'on' the membrane. At least that's what I've been writing.
Not liking the june 2014 f215 paper, apart from the synthesis of a polypeptide 7 marker, the rest is utter balls
Original post by CaliSurf'
Can someone please explain 'action potentials' im getting really pissed off trying to understand that ****. In one narration it says the membrane is impermeable to Na+ but then it says 'Na ion channels open so the membrane becomes more permeable' where have the Na ion channels come from ffs. Any help will be much appreciated.


The membrane has sodium potassium pumps at rest the 3 sodium ions are being pumped out and 2 potassium in this is to ensure that the inside is negatively charged compared to outside by at rest I mean when there is not action potential no neve Impule but when the a nerve impulse is generated then the membrane becomes more permeable so sodium ions start to diffuse into the cell if enough do then another sort of channel opens called voltage gated sodium channel it's tell you in the name that it only opens but a certain voltage when these open loads and loads of sodium will diffuse into the cell making it go to a charge of +40 sodium has a charge of +1 so loads have to diffuse in and that creates an action potential
Original post by Thelostking


Thank you
Original post by Lychees
you could say in myelinated the speed of conduction is much faster because the myelinated sheath is an insulated layer that stops the ions from leaving as they cant diffuse through except at the nodes of ranvier where saltatory conduction happens. something like that :smile:

Okay thanks 😊
Original post by Student23478
What do we need to know abhor kidney failure??? Like the methods is it just renal dialysis??? And what about it

The methods for it and the disadvantaged and advantages of them
And you could possibly get asked to compare them
Original post by 25tiarrific
The OCR textbook has a pretty good comparison table for them in the back, where the spread answers are, stuff like how many Schwann cells per neurone (one loosely wrapped for unmyelinated), function (movement vs digestion and breathing), where they're found, relative lengths and speed of transmission. If you don't have the textbook or can't find it just say! :smile:


Which text book is it ?
Original post by mushyD
Someone tell me what topic areas/questions that could be asked on f214

There tends to be at least one whole questions on each module tbh id say majority of the marks come from the first module though but they could easily change this and give something else
**** exams...
Original post by GianluigiBuffon
**** exams...


hmmm Juve or Barca is the question, I take it your supporting....
Original post by domcandrews
hmmm Juve or Barca is the question, I take it your supporting....

I'm almost tempted to not watch it because unit 4 on monday... :/
Original post by ChoccyPhilly
I'm almost tempted to not watch it because unit 4 on monday... :/


I was the same, mans got one everyday next week, lol but not watching messi perform his magic would be a sin in itself, gonna wake up early tomorrow (say this to myself every single day lol) and work solid until then, and then count that as my 'break'.
Original post by domcandrews
I was the same, mans got one everyday next week, lol but not watching messi perform his magic would be a sin in itself, gonna wake up early tomorrow (say this to myself every single day lol) and work solid until then, and then count that as my 'break'.

My treat was the FA cup final, and boy, was that a treat. I have 5 next week so i've tried to do my best this week as I didnt want to be under the illusion that I have time before it all piles on top of me. Probably for the best to avoid the cup final even if i am prepared. I can just catch the goals somewhere else, unlike my exams.
Original post by ChoccyPhilly
My treat was the FA cup final, and boy, was that a treat. I have 5 next week so i've tried to do my best this week as I didnt want to be under the illusion that I have time before it all piles on top of me. Probably for the best to avoid the cup final even if i am prepared. I can just catch the goals somewhere else, unlike my exams.


Ah fair enough then! Yeah true you make a good point, will see how much I get done before kick off. Don't want to relax too much, then might not be able to do work again for that night, also a problem ah

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